Computing devices of the type commonly called personal computers have been available for over a decade, and typically include a central processing unit which has no alpha-numeric keys but which has a connector, and a keyboard which is physically separate from the central processing unit and which has a cable which can be coupled to the connector of the central processing unit in order to effect an electrical connection therebetween. The keyboard has a plurality of manually operable keys, typically including one set which is similar to a traditional typewriter keyboard, and a further set which controls cursor movement and special functions. This conventional keyboard is relatively lightweight, and many users like to place it in their laps during long computing sessions, while the heavy central processing unit rests on a table or the floor.
More recently, a portable variation of the personal computer has been rapidly gaining popularity and is the so-called "laptop" style, which is relatively compact and lightweight and which typically has a single housing which includes both the central processing unit and a built-in alpha-numeric keyboard. However, the keys for special functions and cursor control are typically not provided as a set of separate keys, but instead are assigned to keys which already serve as keys of the standard typewriter-type set of keys. In order to execute these special control functions, the user must usually use a special control key to tell the system whether the dual function keys are presently being used to control the special functions rather than for their normal purpose, which is relatively cumbersome and inefficient. Further, the weight of a laptop computer is sufficiently large that, despite the "laptop" nickname, it is usually uncomfortable to actually work with it in one's lap for more than a short period of time, and it also becomes uncomfortable if the laptop is placed during extended use on a table or other support surface which is not at a height which is comfortable for using the built-in keyboard.
One commercially available laptop computer, which is shown in FIG. 6 and described in more detail later, has a built-in keyboard, but also has a connector to which can be coupled a custom keypad. A keypad is essentially a portion of a conventional keyboard unit, and typically has only numeric keys and a few keys for special functions and/or cursor control. The custom keypad for this commercially available system has a cable with a plug which can be coupled to the connector on the laptop computer, the connector being intentionally different from that used for conventional keyboards in order to prevent a user from inadvertently plugging in a conventional keyboard unit which this conventional laptop computer is not designed to operate with. Thus, this conventional system solves some but not all of the problems associated with the keys of the typical laptop computer. Nevertheless, the majority of manual operator functions must still be carried out using the alphabetic keys of the built-in keyboard of the device, with the attendant problems discussed above. Further, the external keypad is coupled by the connector on the laptop computer directly to an internal keyboard processor of the laptop computer, and has to effect all communications with the main processor of the laptop computer through the internal keyboard processor.
It is an object of the invention to provide an improved circuit for facilitating use of a given computing device with two separate input sections which each have a plurality of keys, one of the input sections typically being an integral portion of the device and the other being a physically separate unit.
A further object is to provide such an arrangement in which the internal and external input section can include a full typewriter-type set of keys, and in which the external input unit can be either a keyboard having a full typewriter-type set of keys or a keypad having substantially less than a full typewriter-type set of keys, the keys of the keypad augmenting the keys of the internal input section.
A further object is to provide such an arrangement in which the external input section can be a conventional and commercially available keyboard unit.
The objects and purposes of the invention, including those set forth above, are met by providing a computing device which includes a processor, an internal input section which is an integral portion of the device and which includes a plurality of manually operable keys, a connector arrangement which can facilitate electrical connection to the device of an external input unit having a plurality of manually operable keys, a selectively actuable switch which can effect and interrupt an electrical connection between the connector arrangement and the processor, and an arrangement for selectively actuating and deactuating the switch.